For decades optical microscopy has been the workhorse of various fields including engineering, physical sciences, medicine and biology. Despite its long history, until relatively recently, there has not been a significant change in the design and working principles of optical microscopes. Over the last decade, motivated partially by the quest to better understand the realm of the nano-world, super-resolution techniques started a renaissance for optical microscopy by addressing some of the most fundamental limitations of optical imaging such as the diffraction limit. Besides these super-resolution techniques, several other novel imaging architectures were also implemented to improve the state of the art in optical microscopy towards better speed, signal to noise ratio (SNR), contrast, throughput, specificity, etc. This recent progress in microscopy utilized various innovative technologies to overcome the fundamental barriers in imaging and has created significant excitement in a diverse set of fields by enabling new discoveries to be made. However, together with this progress, the overall complexity and the cost of the optical imaging platform relatively increased which limits the wide spread use of some of these advanced optical imaging modalities beyond well equipped laboratories.
In the meantime, a rapid advancement in digital technologies has occurred, with much cheaper two-dimensional solid state detector arrays having significantly larger areas with smaller pixels, better dynamic ranges, frame rates and signal to noise ratios, as well as much faster, cheaper and more powerful digital processors and memories. This on-going digital revolution, when combined with advanced imaging theories and numerical algorithms, also creates an opportunity for optical imaging and microscopy to face another dimension in this renaissance towards simplification of the optical imaging apparatus, making it significantly more compact, cost-effective and easy to use, potentially without a trade-off in its performance. Lenses for decades have been helping detectors (analog or digital) to operate at the lowest possible space-bandwidth product that is determined by the desired field-of-view and the resolution of the image. However, the above discussed digital revolution has already advanced the state of the art for digital imagers such that a 2D space-bandwidth product of >10-20 Million is readily available nowadays. This implies that today's detector arrays are now much better suited to handle the information distortion caused by diffraction, which may then raise questions on the absolute necessity of the use of lenses in optical imaging. Moreover, today's digital processors together with novel algorithms are also in much better shape to process, almost instantaneously, the acquired information at the detector end for taking the job of a physical lens. With this in mind, one can conclude that the widespread use of lenses (or similar wavefront shaping elements) in optical imaging devices can now be potentially replaced for several application needs (specifically for cell microscopy) by cost-effective, compact and much simpler optical architectures that compensate in the digital domain for the lack of complexity of optical components. This approach should especially address the needs and the requirements of cytology, microfluidics, and resource-limited settings, potentially providing a leapfrog in the fight against various global health related problems involving infectious diseases.